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1‐phenyl 5‐mercarpto 1,2,3,4‐tetrazole (PMT) was tested as an inhibitor for the corrosion of steel in 0.5 M H₂SO₄ and 1/3 M H₃PO₄ by weight‐loss and electrochemical methods. Results obtained showed that the inhibition efficiency of PMT increased with the increase of inhibitor concentration and reached an optimum value (98 per cent) at 10⁻³ M in H₂SO₄ and H₃PO₄ solutions. The effect of the temperature on the kinetic parameters of corrosion of steel in the aqueous solutions of H₂SO₄ and H₃PO₄ with and without addition of PMT has been studied and the associated parameters were determined.

To correlate the inhibitory effect of triazole compounds on the corrosion of copper in HCl at various temperatures by semi‐empirical molecular orbital theory.

Two triazoles were selected as the best inhibitors among the triazole compounds tested. Gravimetric and electrochemical measurements were conducted.

Correlation between inhibition efficiency and calculation of molecular orbital of triazole compounds was obtained. Cu(I)‐triazole complex formation was confirmed by UV spectroscopy.

The calculation of energetic levels of molecular orbital may be a tool to explain the classification of inhibitor efficiency.

The theoretical calculation is a complementary mean to selecting an efficient inhibitor among a given series. Good agreement between the experimental methods explored and theoretical calculations was observed.

The originality of this work was the finding of the correlation between energetic levels of orbital molecular and inhibitor efficiency of triazole compounds. The confirmation of the formation of Cu(I)‐triazole by UV‐visible spectroscopy was also new.

To evaluate the effect of some tetrazole compounds as corrosion inhibitors of copper in HNO₃ at various temperatures.

1‐phenyl‐5‐mercapto‐1,2,3,4‐tetrazole (PMT) was selected as the best inhibitor among the tetrazole compounds tested. Gravimetric and electrochemical techniques were conducted.

PMT was an excellent inhibitor for copper in acid. Its efficiency attained 97.5 per cent and decreased slightly with temperature.

The inhibition efficiency increased with the concentration of PMT to reach 97.5 per cent at 10⁻³ M. Good agreement between the various methods explored was observed. Polarisation measurements also showed that PMT acted as a mixed inhibitor.

The efficiency of PMT increased with the concentration but decreased with rise of temperature in the 298‐333 K range. As such, PMT could be used in chemical cleaning and pickling processes.

The originality of this work was the finding of an efficient inhibitor (PMT) having a nearly 100 per cent efficiency.

The inhibition of the copper corrosion in aerated 3 per cent sodium chloride solution was studied by using electrochemical polarisation, weight loss and impedance measurements in the presence of different concentration of synthesised bipyrazolic compounds: N,N‐bis (3,5‐dimethylpyrazol‐1‐ylmethyl) butylamine (bipy1); N,N‐bis (3,5‐dimethylpyrazol‐1‐ylmethyl) allylamine (bipy2); N,N‐bis (3,5‐dimethylpyrazol‐1‐ylmethyl) ethanolamine. (bipy3); N,N‐bis (3,5‐dimethylpyrazol‐1‐ylmethyl) cyclohexylamine (bipy4); N,N‐bis (3‐carbomethoxy‐5‐methylpyrazol‐1‐ylmethyl) cyclohexylamine (bipy5); N,N‐bis(3‐carboethoxy‐5‐methylpyrazol‐1‐ylmethyl) cyclohexylamine (bipy6). The inhibition efficiencies obtained from cathodic Tafel plots, polarisation resistance and weight loss are in good agreement with electrochemical impedance spectroscopy (EIS) measurements. All these additives were found to be excellent inhibitors of copper corrosion. The difference in inhibition efficiencies of these inhibitors was not big, but the optimum concentration for maximum efficiency was slightly dependent on the substitution of each molecule. The studied molecules act as mixed‐type inhibitors. Detailed study of bipy1 shows that the maximum inhibition efficiency revolves around 99 per cent from 5×10⁻⁴ M of inhibitor. This latter adsorbs on the copper surface according to the Frumkin isotherm model. The inhibition efficiency of bipy1 decreases with the rise of temperature in the range 25 – 60°C.

The inhibition of the corrosion of the mild steel in 1M HCl by new bipyrazolic compounds has been studied by weight loss, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. Results obtained reveal that these compounds are very good inhibitors. The inhibition efficiency increases with the increase of inhibitor concentration and reached 94 at 10^–3M for the bipyrazoles studied. Potentiodynamic polarisation studies clearly reveal that the presence of the bipyrazoles does not change the mechanism of the hydrogen evolution reaction and they act essentially as cathodic inhibitors. The effect of temperature on the corrosion behaviour of mild steel in 1M HCl without and with the bipyrazoles at 10^–3M was studied in the temperature range from 298° to 343°K. EIS measurements show the increase of the transfer resistance with the inhibitor concentration.

The effects of the addition of poly(4‐vinylpyridine) (P4VP) and its derivative poly(4‐vinylpyridine poly‐3‐oxide ethylene) (P4VPPOE) on the corrosion of Cu60‐Zn40 in 0.5M HNO₃ have been investigated by potentiodynamic and weight loss measurements. Both of the studied polymers decrease the corrosion rate. Their inhibition efficiency (E%) increases with the concentration. The maximum of inhibition was obtained for P4VPPOE (100 per cent at 10^–5M). E% obtained from cathodic Tafel plots and weight loss methods were in good agreement. The inhibitors were adsorbed on the Cu60‐Zn40 surface according to the Frumkin adsorption isotherm model. P4VPPOE acts as a cathodic inhibitor and its efficiency is temperature independent.

The purpose of this investigation is the evaluation of the inhibitive performance of a new “gemini” surfactant in the series of bis‐quat: N, N, N′, N″, N″‐pentamethyl diethyleneamine‐N, N″‐di‐[tetradecylammonium bromide] on the corrosion of iron in 1 M HCl by gravimetric, potentiodynamic and electrochemical impedance measurements. The effect of the temperature on the corrosion behavior of iron in 1 M HCl without and with inhibitor is studied in the temperature range (298‐333 K). This work also attempts to correlate thermodynamic and kinetic parameters with the inhibition effect.

The inhibition efficiency of gemini synthesized is investigated by weight loss, potentiodynamic polarization and impedance spectroscopy methods.

The synthesized gemini bis‐quat acted as a good inhibitor in 1 M HCl, and inhibition efficiency increased with inhibitor concentration and temperature. Polarization curves showed that the surfactant was a mixed‐type inhibitor in hydrochloric acid. Impedance spectroscopy measurements showed that the inhibitor acted through the formation of a multilayer film at the iron surface. The adsorption of inhibitor on the iron surface obeyed the Langmuir adsorption isotherm equation. The inhibition effect was satisfactorily explained by both thermodynamic and kinetic parameters.

The adsorption of surfactants in the metal surface can markedly change the corrosion resisting property of the metal. So the study of the relation between the adsorption and corrosion inhibition is of a great importance. This was the first attempt to study the inhibition properties of gemini surfactants at the host laboratory.

The cycloaddition of cyclic nitrone1‐pyrroline‐1‐oxide with 1‐dodecene and 1‐hexadecene afford a bicyclic (isoxazolidines). These isoxazolidines were tested for corrosion inhibition of carbon steel in 1N H₂SO₄ in the 30‐60°C temperature range by gravimetric and electrochemical methods. The compound isoxazolidines exhibited excellent inhibition efficiency in the acidic corrosion environment. The presence of heteroatoms such as N and O induce greater adsorption of the inhibitor molecules onto the surface of carbon steel and the long hydrocarbon chains ensure coverage of the metal surface. The values of activation energy and free energy of adsorption indicated the physical nature of the adsorption on the surface of the carbon steel. Thermodynamic parameters were determined for the adsorption process (ΔG_ads^o, ΔH_ads^o, ΔS_ads^o), and kinetic parameters for the metal dissolution (or hydrogen evolution) reaction in the presence of the isoxazolidines. The adsorption of inhibitors on the metal surface was found to obey the Langmuir adsorption isotherm. The isoxazolidines were found to be mixed‐type inhibitors. The isoxazolidine which had a tetradecyl hydrophobe was found to be a better inhibitor than was the decyl analogue.

The inhibition effect of some non‐ionic surfactants Tween 20, Tween 40, Tween 60, Tween 80 and O1 (EO)₂₀ on steel in acidic chloride solution has been investigated by studying their adsorption behaviour and the use of the gravimetric method in order to determine the inhibition efficiency. The results obtained show that these compounds are very good inhibitors. High inhibition efficiency is observed around their critical micelle concentrations (CMC), and it increases with the number of carbon atoms in the chain length of their molecules.

The purpose of this paper is to study the effect of silicon and phosphorus content in steel suitable for galvanizing on its corrosion and inhibitor adsorption processes in steels/cetyltrimethylammonium bromide combined and KI (mixture)/5.0 M hydrochloric acid systems has been studied in relation to the temperature using chemical (weight loss), Tafel polarization, electrochemical impedance spectroscopy (EIS), scanning electronic microscope (SEM) analysis and Optical 3D profilometry characterization. All the methods used are in reasonable agreement. The kinetic and thermodynamic parameters for each steels corrosion and inhibitor adsorption, respectively, were determined and discussed. Results show that the adsorption capacity for Steel Classes A and B are better than Steel Class C surfaces depending on their silicon and phosphorus content. Surface analyses via SEM and Optical 3D profilometry was used to investigate the morphology of the steels before and after immersion in 5.0 M HCl solution containing mixture. Surface analysis revealed improvement of corrosion resistance of Steels Classes A and B in the presence of mixture more than Classes C. It has been determined that the adsorbed protective film on the steels surface heterogeneity markedly depends on steels compositions, that is, the heterogeneity increases with decreasing silicon and phosphorus content.

The effect of silicon and phosphorus content in Steels Classes A, B and C on its corrosion and inhibitor mixture adsorption processes in 5.0 M HCl solution has been studied by weight loss, potentiodynamic polarization, EIS and surface analysis.

The inhibition efficiency of mixture follows the order: (Steel Class A) > (Steel Class B) > Steel Class C) and depends on their compositions in the absence of mixture according on their silicon and phosphorus content, that is, the corrosion rate increases with increasing of the silicon and phosphorus content. A potentiodynamic polarization measurement indicates that the mixture acts as mixed-type inhibitor without changing the mechanism of corrosion process for the three classes of mild steels.

Corrosion rate mild steels in 5.0 M HCl depends on their compositions in the absence of mixture according to their silicon and phosphorus content, that is, the corrosion rate increases with increasing silicon and phosphorus content. The adsorbed protective film on the steels surface heterogeneity markedly depends on steels class’s compositions, that is, the heterogeneity increases with decreasing silicon and phosphorus content.